PLM glossary
The vocabulary this site uses, defined by somebody who has to live with the distinctions. Where a term earns its place by being different from a term people confuse it with, that is the part written down.
A
Alternate
A part that may be used in place of another at a specific position in a structure, approved by engineering for that use.
Not the same as a substitute or an AML alternate. An alternate is position-specific, a substitute is generally interchangeable, and an AML alternate is a different manufacturer part for the same internal part. Three different decisions with three different approvers.
AMLApproved Manufacturer List
The set of manufacturer parts engineering has qualified for a given internal part, each with an approval state.
Distinct from the AVL. The AML answers what may be built with; the AVL answers who it may be bought from. Component lifecycle risk attaches to the AML, because a feed knows manufacturer part numbers and has never heard of your internal one.
As-built
The configuration a specific serialised unit was actually built to, as opposed to what the current design says.
The question a warranty claim asks. Reconstructing it from work orders gives you what was consumed rather than what was specified, and if a floor substitution was recorded as the original, the reconstruction is confidently wrong.
AVLApproved Vendor List
The suppliers approved to sell you a given part — a commercial relationship with terms, pricing and a vendor part number.
Usually mastered in the ERP, because it is a purchasing fact rather than an engineering one.
B
Baseline
A named, frozen resolution of a structure at a moment — a qualification, a first article, a released configuration.
Distinct from a snapshot or an export. A baseline is a first-class object you can compare against later, which is what a customer qualification actually needs.
BOMBill of materials
The structure describing what a product is made of, in what quantity, in what relationship, under what conditions and at what revision.
Not a parts list. The extra clauses are what let one structure hold several correct answers at once — which is the entire subject.
C
CAPACorrective and Preventive Action
The recorded response to a quality issue: what caused it, what was changed, and evidence that the change worked.
The last clause is the one systems make optional. A CAPA closed without verification evidence gets raised again next year by somebody who does not know it already was.
Controlled copy
A copy of a released document issued to a named recipient, watermarked, with an expiry, and recorded in a register.
The register is the point. Watermarking is easy; knowing who is still holding rev C when rev D releases is the question that actually gets asked.
D
Deviation
Permission to ship off-specification within stated bounds, for a stated period or quantity, agreed in advance.
Does not change the design. Modelling it as a change order with a flag makes the released design history unreadable.
Digital thread
The graph of typed relationships connecting requirements, documents, CAD, parts, structures, changes and suppliers.
Nobody maintains a thread. It is what the records already are, provided the relationships were recorded as objects rather than mentioned in a drawing note.
E
EBOMEngineering bill of materials
The structure as engineering owns it: what the product is, by design.
Diverges legitimately from the MBOM over phantoms, packaging, regional substitutions and assembly sequence.
ECNEngineering Change Notice
The communication that a change has been released — who needs to know, and what they need to do about it.
ECOEngineering Change Order
The instruction stating exactly what changes, which objects are affected, which revisions result, and when it takes effect.
An ECO with no effectivity is an ECO that takes effect on approval, which makes every phased cutover a manual reconciliation.
ECREngineering Change Request
The question of whether something should change, carrying the justification and the alternatives considered.
The alternatives are the valuable part. A change process that discards rejected options loses the reasoning six months later.
Effectivity
The condition under which a BOM line is part of the product — a date range, a unit-number range, a plant, or a combination.
Not a revision and not a lifecycle state. It is how one structure holds both the old and new component as correct answers during a phased cutover.
F
Floating reference
A BOM line naming a part without naming a revision, letting revision policy decide which one applies.
The opposite of a pinned reference. Both are legitimate; not knowing which a given line uses is not.
I
Iteration
Work in progress inside the revision currently being made, private to a workspace.
Nothing outside can reference an iteration, which is exactly what makes it safe to be wrong in one.
L
Lifecycle state
Where an object sits in its approval progression — draft, in review, released, superseded, obsolete.
Orthogonal to revision. A revision moves through states; a new revision starts a fresh pass. Conflating them makes revision B, under obsolescence review inexpressible.
M
MBOMManufacturing bill of materials
The structure a specific plant builds from, derived from the EBOM with a traceable relationship back to it.
Ownership is genuinely contested and frequently belongs in the ERP. It should be decided per organisation rather than assumed by a vendor.
MPNManufacturer part number
The number the manufacturer of a component uses for it — the identifier the outside world knows.
Component data feeds match on this and only this. A house number with no AML entry behind it is invisible to every lifecycle feed there is.
N
NCRNonconformance report
A record that something did not meet specification, with the quantity, the part at its revision, and what was decided.
P
Phantom
An assembly that exists in engineering and not in the world — referenced as one line, never purchased as one thing.
A fastener kit is the usual example. Phantoms explode into components in the MBOM, which is one of the four reasons the two structures legitimately differ.
Pinned reference
A BOM line naming an exact revision of a child part, which never moves regardless of later releases.
R
Reference designatorRef des
The identifier naming where each instance of a component goes — R1, R2, C14, U7.
The count should equal the quantity. When it does not, one of the two is wrong, and it is a cheap check that is almost never automated.
Resolution
Turning a stored structure plus a set of conditions — date, unit, plant, options, revision policy — into exactly one configuration.
The operation most PLM tools leave to the person reading the screen, which is why their cost report and compare screen can disagree.
Revision
A released state of an object that other things reference — a BOM line, a drawing, a qualification, a shipped unit.
Immutable once released. If it could be edited, everything referencing it would silently change meaning.
Rollup
Summing a value — cost, mass, a substance concentration — up through a resolved structure to a total for the product.
Only meaningful over resolved lines. A rollup across everything stored counts components from configurations nobody builds.
S
SCARSupplier Corrective Action Request
A formal request to a supplier to investigate a problem and state what they have changed to prevent recurrence.
Scrap factorYield loss
The expected difference between the quantity issued and the quantity that ends up in the product.
Where the factor lives — engineering quantity or manufacturing quantity — is a real modelling decision, not a detail.
Stop ship
An instruction to halt shipment of an affected product immediately, pending investigation.
Shares a lifecycle with the other change kinds but changes no design. Its value is that it is a record with an owner and a time, not an email.
Substitute
A part generally interchangeable with another wherever it appears, rather than at one specific position.
System of record
For a given object or field, the one system that owns it and wins when two systems disagree.
Exactly one per object, never both. An object with two masters is a data-loss incident waiting for a scheduling coincidence.
U
Unit effectivitySerial effectivity
Effectivity keyed to serial number rather than to the calendar — this line applies from unit 1400 onward.
The only honest way to answer a field service question about a machine built two years ago, regardless of what the calendar says now.
V
Variant
One valid combination of option values — 240 volt, IP67, German — resolving to a specific structure.
Not a separate product. Copying a structure per variant means a change gets applied to most of the copies and forgotten on the rest.
W
WaiverConcession
Acceptance of a specific non-conformance after the fact, for a defined quantity already produced.
A deviation is agreed in advance; a waiver accepts something that has already happened. Neither changes the design.
Where-used
The inverse of a bill of materials: given a part, which structures reference it and which products they roll up to.
Single-level and multi-level give different answers, and both differ from a text search for the part number. The scope is the answer.
Workspace
A private context in which an engineer can edit objects without anyone downstream seeing the work in progress.
What makes it safe to restructure an assembly across a week rather than in one nervous sitting.